This invention relates to a workpiece transferring mechanism of a forming press which includes a plurality of workpiece holding members each reciprocating between two dies to transfer a workpiece from one die to the other die, crank mechanisms to actuate said workpiece holding members to move between a clamping position and a releasing position, and a swinging mechanism connected to the workpiece holding members and the crank mechanisms so as to swing the workpiece holding members and to swing the crank mechanisms synchronously with the workpiece holding members. Particularly, the invention relates to a swinging mechanism of the forming press.
A known press for forming nuts is shown in FIGS. 1 to 4. The press comprises five workpiece holding members B (only one workpiece holding member B is shown in the drawings in detail; the remaining is omitted) whose top ends are respectively connected to crank mechanisms with bolts B1. Each crank mechanism has a first crank A4, a second crank A2 and a cam A1 and actuates each workpiece holding member B to alternately perform clamping and releasing operations. The second cranks A2 are aligned and are turnable about a common horizontal axis A21. The input end of the cranks A2 are actuated by the cam A1 and the output ends thereof are provided with bolts A22 and arranged above the input ends A41 of the cranks A4 to depress the same. A pneumatically operated plunger E2 of a pneumatic cylinder El which is mounted on a stationary part E of the machine pushes upward the input end of each crank A4 so that the input end of each crank A4 is movably clamped between the plunger E2 and the output end of each crank A2 and is turnable about a vertical axis while being moved upward and downward by the crank A2. The output end A42 of each crank A4 is connected to the top end of each workpiece holding member B. The upward and downward movement of the cranks A4 actuates the clamp portions B8 of the workpiece holding members to alternately clamp and release the workpieces F.
The cranks A4 are aligned and mounted pivotally on a common reciprocating elongated crank support member C3 which swings the cranks A4 simultaneously. An elongated swinging member C2 is provided longitudinally below the crank support member C3. Two levers C23 are mounted in the two end portions of the swinging member C2. Pivot rods C22 are used to connect one ends of the levers C23 to the end portions of the swinging member C2. The other ends of the levers C23 are pivoted to a stationary machine frame with pivot members E3. The crank support member C3 is mounted on the levers C23 with mounting rods C21. The supports E3 are arranged in alignment with the input ends of the cranks A4. The swinging member C2, the levers C23 and the machine frame form a parallelogram linkage system in which the swinging member C2 is reciprocated by the reciprocating drive rod C1. When the swinging member C2 is moved by the drive rod C1, the levers C23 reciprocate accordingly so that the crank support member C3 moves synchronously with the swinging member C2. As a result, the workpiece holding members B are moved between adjacent dies D and the cranks A4 move synchronously with the workpiece holding members B to actuate the same to perform clamping and releasing operations. Each workpiece holding member B has a gear B3 engaging a slightly curved rack member B2 so that the workpiece holding member B is moved along a proper path.
FIG. 5 shows schematically the parallelogram linkage system comprising one of the cranks A4, one of the levers C23, the crank support member C3. From the figure, it can be noted that the distance "b", i.e. the distance that the swinging member needs to travel is longer than that the crank support member C3 needs to travel. Since the levers C23 are long in order to optimize the applied force required to swing the cranks A4 and the workpiece holding members b, the drive rod C1 has to reciprocate with a long amplitude, thereby reducing the speed of the swinging member. On the other hand, the two end portions of the swinging member must be of large volume to receive the long levers C23, thereby requiring considerable energy consumption to operate the swinging mechanism.